The central aim of the proposed research is to assess the viability of Modulated Imaging as a method that will provide objective functional parameters that can be used to determine status of tissue reconstruction flaps under conditions of venous and arterial occlusion and in response to reperfusion using hypertonic -hyperoncotic saline solutions. The use of tissue transfer flaps is a method of moving tissue from a donor location to recipient location and re-attaching the arteries &veins to the blood vessels at the recipient site. The medical utility of this process is to allow for reconstructive surgery after trauma, as well as after surgical resection of cancer. This type of surgery is subject to failure however, which may be due to1) vascular insufficiency caused by to mechanical obstruction of the artery or vein;2) injury caused to the transferred tissues due to the lack of blood flow when a free tissue flap is performed;or 3) due to ischemia-reperfusion (I/R) injury, which results after blood flow has been returned to the transferred tissue. The first postoperative days after free tissue transfer are characterized by the risk of microvascular complications and loss of transferred tissue by necrosis. Loss of a tissue transfer flap is a devastating experience to both the surgeon and the patient. Strategies for reducing flap loss involve both development of new technologies that detect flap compromise and the use of fluids that minimize ischemia-reperfusion injury. Early in the era of microsurgery, flap monitoring was performed based on clinical observation of skin color, capillary refill, and dermal bleeding. In fact, this remains the standard of care. However, issues related to staffing and subjective variations related to making a clinical determination of a flap's perfusion have led to the search for objective methods of assessment of flap status. One promising technology for measuring tissue oxygenation in-vivo is Modulated Imaging (MI). MI is a noncontact imaging approach based on diffuse optical spectroscopy principles that employs patterned illumination. MI enables rapid quantitative determination of the optical properties over a wide field-of-view. When combined with multi-spectral imaging, MI can quantify in-vivo concentrations of chromophores that are relevant to flap health, namely, oxy- and deoxy-hemoglobin and water concentration. We present results of a preliminary in-vivo MI study using a rodent dorsal skin pedicle flap model. This allowed us to evaluate the feasibility of MI to deduce spatially resolved maps of tissue hemoglobin, oxygenation and hydration. Here we propose that MI can be used for quantitative assessment of flaps in response to vascular occlusion and reperfusion with the aid of hypertonic-hyperoncotic saline solutions. The results of the proposed research will inform further investigations involving MI within the domain of tissue transfer flaps, with the ultimate objective of developing and deploying this technology in the clinical domain. PUBLIC HEALTH RELEVANCE: The use of tissue transfer flaps is a method of moving tissue from a donor location to recipient location and re-attaching the arteries &veins to the blood vessels at the recipient site. This type of reconstructive surgery is subject to failure however, which may include complications due to ischemia-reperfusion injury and vascular insufficiency. We propose to test a new imaging device that will have the capability to guide reconstructive surgery and post-surgical recovery, both reducing post-surgery morbidity and reducing uncertainty in flap healing. Ultimately, if shown to be effective, this technology may lead to reduced duration of hospital stay and concomitant heath care costs in addition to improving surgical outcomes.